<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>ex06</title>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.4.1/dist/css/bootstrap.min.css"
        integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
    <style>
        html,
        body {
            font-size: 15px;
        }

        form {
            width: 30rem;
        }

        .login-content{
            height: 100vh;
        }
    </style>
</head>

<body>
    <div class="d-flex justify-content-center">
        <div class="d-flex align-items-center login-content">
            <form>
                <h3 class="d-flex justify-content-center">用户登录</h3>
                <div class="form-group">
                    <label for="userName">用户名</label>
                    <input type="text" class="form-control is-invalid" id="userName" aria-describedby="输入用户名"
                        name="userName">
                    <div class="valid-feedback">
                        用户名格式正确
                    </div>
                    <div class="invalid-feedback">
                        用户名不可用
                    </div>
                </div>
                <div class="form-group">
                    <label for="password">密码</label>
                    <input type="password" class="form-control is-valid" id="password" name="password">
                    <div class="valid-feedback">
                        密码可用
                    </div>
                    <div class="invalid-feedback">
                        密码必须>5位
                    </div>
                </div>
                <button type="submit" class="btn btn-primary btn-block">提交</button>
            </form>
        </div>
    </div>
</body>

</html>